Semiconductor device and its manufacturing method

ABSTRACT

In a fabrication method of a semiconductor device including a plurality of silicon-based transistors or capacitors, there exist hydrogen at least in a part of a silicon surface in advance, and the hydrogen is removed by exposing the silicon surface to a first inert gas plasma. Thereafter, plasma is generated by a mixed gas of a second inert gas and one or more gaseous molecules, and a silicon compound layer containing at least a part of the elements constituting the gaseous molecules is formed on the surface of the silicon gas.

TECHNICAL FIELD

The present invention relates to a semiconductor device in which anoxide film, a nitride film, an oxynitride film, or the like, is formedon a silicon semiconductor, and the fabrication method thereof.

BACKGROUND ART

The gate insulation film of a MIS (metal/insulator/silicon) transistoris required to have various high-performance electric properties andhigh reliability characteristics, such as low leakage currentcharacteristics, low interface state density, high breakdown voltage,high resistance against hot carriers, and uniform threshold voltagecharacteristics.

The thermal oxidation technology using oxygen molecules or watermolecules at approximately 800° C. or more has been used conventionallyas the formation technology of the gate insulation film that satisfiesthe above requirements.

A thermal oxidation process has been conducted conventionally afterconducting a cleaning process of removing surface contaminants, such asorganic materials, metals, and particles, as a preprocessing process. Insuch a conventional cleaning process, cleaning using a dilutedhydrofluoric acid or hydrogenated water, for example, is performed atlast, for terminating the dangling bonds existing on the silicon surfaceby hydrogen. Thereby, formation of a native oxide film on the siliconsurface is suppressed, and the silicon substrate thus having a cleansurface is forwarded to the following thermal oxidation process. In thethermal oxidation process, the terminated hydrogen at the surfaceundergoes decoupling during the process of raising the temperature ofthe silicon substrate in an inert gas atmosphere of argon (Ar), forexample at a temperature equal to or more than 600° C., approximately.Then, oxidization of the silicon surface is conducted at approximately800° C. or more in an atmosphere to which oxygen molecules or watermolecules are introduced.

Conventionally, in a case where a silicon oxide film is formed on thesilicon surface by using such a thermal oxidization technique,satisfactory oxide film/silicon interface characteristics, highbreakdown voltage of the oxide film, leakage-current characteristics,and the like, are achieved only in the case where a silicon surfacehaving the (100) orientation is used. Further, remarkable degradation ofleak current occurs in the case where the thickness of the silicon oxidefilm formed by the conventional thermal oxidation process is reduced toapproximately 2 nm or less. Thus, it has been difficult to realize ahigh-performance miniaturized transistor that requires decrease of thegate insulation film thickness.

Further, in a crystal silicon having a surface orientation other thanthe (100) orientation or a polycrystalline silicon generally having aprimarily (111)-oriented surface on an insulation film, interface statedensity at the oxide film/silicon interface is remarkably high ascompared with the silicon oxide film formed on the (100)-orientedsilicon even when the silicon oxide film is formed by using the thermaloxidation technology. Thus, a silicon oxide film having a reduced filmthickness possesses poor electric properties in terms of breakdowncharacteristics, leakage current characteristics, and the like. Hence,there has been a need of increasing the film thickness of the siliconoxide film when using such a silicon oxide film.

Meanwhile, the use of large-diameter silicon wafer substrate orlarge-area glass substrate is increasing these days for improving theefficiency of semiconductor device production. In order to formtransistors on the entire surface of such a large-size substrate withuniform characteristics and with high throughput, an insulation filmforming process conducted at a low temperature so as to decrease themagnitude of the temperature change in heating or cooling and, further,having small temperature dependence is required. In the conventionalthermal oxidation process, there has been a large fluctuation ofoxidation reaction rate with respect to temperature fluctuation, and ithas been difficult to produce semiconductor devices with high throughputwhile using a large-area substrate.

In order to solve these problems associated with the conventionalthermal oxidation technology, multitudes of low-temperature filmformation processes have been attempted. Among others, the technologydisclosed in Japanese Laid-Open Patent Publication No. 11-279773 or thetechnology disclosed in Technical Digest of International ElectronDevices Meeting, 1999, pp. 249-252, or in 2000 Symposium on VLSITechnology Digest of Technical Papers, pp. 76-177, describes a processin which an inert gas is introduced into plasma together with gaseousoxygen molecules, thereby effectively causing the inert gas having alarge metastable level to conduct the atomization of the oxygenmolecules. Hence, relatively good electronic properties are achieved.

In these technologies, a microwave is irradiated to the mixed gas formedof krypton (Kr) that is an inert gas and an oxygen (O₂) gas, the mixedplasma of Kr and O₂ is generated, and a large amount of atomic stateoxygen O* are formed. Then, the oxidation of silicon is conducted at atemperature of about 400° C., and low leakage current characteristics,low interface state density, and high breakdown voltage comparable tothose of the conventional thermal oxidation are achieved. Further,according to this oxidation technology, a high-quality oxide film isobtained also on the silicon surface having a surface orientation otherthan the (100) surface.

However, in such a conventional silicon oxide film formation technologyusing the microwave-excited plasma, in spite of the fact that theoxidation is conducted by using atomic state oxygen O*, only a siliconoxide film having electric properties comparable to those obtained bythe conventional thermal oxidation process that uses oxygen molecules orwater molecules is obtained. Particularly, it has been impossible toobtain the good low leakage current characteristics in the silicon oxidefilm having a thickness of approximately 2 nm or less on the siliconsubstrate surface. Thus, it has been difficult to realizehigh-performance, miniaturized transistors that require further decreaseof the gate insulation film thickness, similarly to the case ofconventional thermal oxide film formation technology.

Further, there has been a problem that degradation of conductance causedby hot carrier injection into the oxide film of a transistor, ordegradation of electric properties with time such as increase of leakagecurrent, in a device that causes tunneling of electrons through thesilicon oxide film as in the case of a flash memory, occur morenoticeably than in the case where the silicon oxide film is formed bythe conventional thermal processes.

DISCLOSURE OF THE INVENTION

Accordingly, a general object of the present invention is to provide anovel and useful semiconductor device and a fabrication method thereofin which the problems described above are eliminated.

A more specific object of the present invention is to provide alow-temperature plasma oxidation technology as an alternative to theconventional thermal oxidation technology.

Another object of the present invention is to provide high-qualityinsulation film formation technology at low temperatures that can beapplied to silicon surfaces of every orientation.

Still another object of the present invention is to provide reliable,high performance, and miniaturized semiconductor devices using suchhigh-quality insulation film formation technology at low temperatures,particularly, transistor integrated circuit device, flash memorydevices, and three dimensional integrated circuit devices provided witha plurality of transistors or various function elements, and to providea fabrication method thereof.

A further object of the present invention is to provide a semiconductordevice comprising a silicon compound layer formed on a silicon surface,

wherein the silicon compound layer contains at least a predeterminedinert gas and has a hydrogen content of 10¹¹/cm² or less in terms ofsurface density.

Another object of the present invention is to provide a semiconductormemory device comprising, on a common substrate, a transistor includinga polysilicon film formed on a silicon surface via a first siliconcompound layer, and a capacitor including a second silicon compoundlayer formed on a polysilicon surface,

wherein each of the first and second silicon compound layers contains atleast a predetermined inert gas and has a hydrogen content of 10¹¹/cm²or less in terms of surface density.

Another object of the present invention is to provide a semiconductordevice having a polysilicon layer or amorphous silicon layer formed on asubstrate as an active layer,

wherein a silicon compound layer containing at least a predeterminedinert gas and having a hydrogen content of 10¹¹/cm² or less in terms ofsurface density is formed on a surface of the silicon layer, and

the semiconductor device drives a display device formed on thesubstrate.

Another object of the present invention is to provide a fabricationmethod of a semiconductor device on a silicon surface, including thesteps of:

exposing the silicon surface to a first plasma of a first inert gas soas to remove hydrogen existing on at least a part of the silicon surfacein advance; and

generating a second plasma of a mixed gas of a second inert gas and oneor a plurality of kinds of gaseous molecules, and forming, on thesilicon surface, a silicon compound layer containing at least a part ofelements constituting the gaseous molecules under the second plasma.

Another object of the present invention is to provide a fabricationmethod of a semiconductor memory device having, on a common substrate, atransistor including a polysilicon film formed on a silicon surface viaa first insulation film and a capacitor including a second insulationfilm formed on a polysilicon surface, including the steps of:

exposing the silicon surface to a first plasma of a first inert gas soas to remove hydrogen existing on at least a part of the silicon surfacein advance; and

generating a second plasma of a mixed gas of a second inert gas and oneor a plurality of kinds of gaseous molecules, and forming, on thesilicon surface, a silicon compound layer containing at least a part ofelements constituting the gaseous molecules as the first insulation filmunder the second plasma.

Another object of the present invention to provide a fabrication methodof a semiconductor device having a polysilicon layer or amorphoussilicon layer on a substrate as an active layer, including the steps of:

forming, on said substrate, a silicon layer formed by said polysiliconlayer or amorphous layer;

exposing a surface of said silicon layer to a plasma of a first inertgas so as to remove hydrogen existing on at least a part of said surfaceof said silicon layer; and

generating a plasma of a mixed gas of a second inert gas and one or aplurality of kinds of gaseous molecules and forming, on said surface ofsaid silicon layer, a silicon compound layer including at least a partof elements constituting said gaseous molecules.

According to the present invention, it becomes possible to completelyremove surface-terminating hydrogen even at low temperature of about400° C. or less in continuous processing without breaking vacuum andwithout degrading the planarity of a silicon surface. Hence, it ispossible to form a silicon oxide film, silicon nitride film, and siliconoxynitride film, having characteristics and reliability superior tothose of a silicon oxide film formed by a conventional thermal oxidationprocess or microwave plasma processing, on a silicon of any surfaceorientation at low temperature of about 500° C. or less. Consequently,it becomes possible to realize a miniaturized transistor integratedcircuit having high reliability and high performance.

Also, according to the present invention, it becomes possible to form athin and high-quality silicon oxide film, silicon nitride film, andsilicon oxynitride film having good characteristics such as leakagecurrent and breakdown voltage even on a silicon surface of a corner partof a device isolation sidewall of, for example, a shallow-trenchisolation or on a silicon surface having a surface form with projectionsand depressions. Consequently, it becomes possible to achievehigh-density device integration with a narrowed device isolation widthand high-density device integration having a three-dimensionalstructure.

In addition, by using the gate insulation film of the present invention,it was possible to realize-a flash memory device and the like capable ofsignificantly increasing the number of times of rewriting.

Further, according to the present invention, it becomes possible to forma high-quality silicon gate oxide film and silicon gate nitride filmeven on a polysilicon formed on an insulation film and having apredominantly (111)-oriented surface. As a result, it becomes possibleto realize a display apparatus that uses a polysilicon transistor havinghigh driving ability, and further, a three-dimensional integratedcircuit device in which a plurality of transistors or functional devicesare stacked.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1 is a conceptual diagram of a plasma apparatus that uses a radialline slot antenna;

FIG. 2 is a characteristic diagram showing the dependence of the bondformed between the surface-terminating hydrogen at a silicon surface andsilicon on the exposure to Kr plasma as measured by an infraredspectroscopy;

FIG. 3 is a characteristic diagram showing the dependence of siliconoxide film thickness on the gas pressure of the processing chamber;

FIG. 4 is a characteristic diagram showing the depth distributionprofile of the Kr density in the silicon oxide film;

FIG. 5 is a characteristic diagram showing the current versus voltagecharacteristic of the silicon oxide film;

FIG. 6 is a diagram showing the relationship between the leakage currentcharacteristics of the silicon oxide film and the silicon oxynitridefilm, and the film thickness;

FIG. 7 is a characteristic diagram showing the dependence of the siliconnitride film thickness on the gas pressure of the processing chamber;

FIG. 8 is a characteristic diagram showing the photoemission intensityof atomic state oxygen and atomic state hydrogen at the time offormation of the silicon oxynitride film;

FIG. 9 is a characteristic diagram showing the elemental distribution inthe silicon oxynitride film;

FIG. 10 is a characteristic diagram showing the current versus voltagecharacteristic of the silicon oxynitride film;

FIGS. 11A-11C are conceptual cross-sectional views of the shallow trenchisolation;

FIG. 12 is a cross-sectional view of a three-dimensional transistorformed on a silicon surface having projections and depressions;

FIG. 13 is a schematic diagram of a cross-sectional structure of a flashmemory device;

FIG. 14 is a schematic cross-sectional view for explaining thefabrication method of the flash memory device of the present inventionstep by step;

FIG. 15 is a schematic cross-sectional view for explaining thefabrication method of the flash memory device of the present inventionstep by step;

FIG. 16 is a schematic cross-sectional view for explaining thefabrication method of the flash memory device of the present inventionstep by step;

FIG. 17 is a schematic cross-sectional view for explaining thefabrication method of the flash memory device of the present inventionstep by step;

FIG. 18 is a schematic diagram of a cross-sectional structure of a MOStransistor formed on a metal substrate SOI;

FIG. 19 is a conceptual diagram of a plasma apparatus accommodated to aglass substrate or plastic substrate;

FIG. 20 is a schematic diagram of a cross-sectional structure of apolysilicon transistor on an insulation film; and

FIG. 21 is a conceptual diagram of a cross-sectional structure of athree-dimensional LSI.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, various preferable embodiments in which the presentinvention is applied will be explained in detail with reference to thedrawings.

First Embodiment

First, a description will be given of an oxide film formation at lowtemperatures by using plasma.

FIG. 1 is a cross-sectional view showing an example of a plasmaprocessing apparatus used in the present invention and using a radialline slot antenna.

In this embodiment, in order to remove the hydrogen terminating thedangling bonds at a silicon surface, Kr, which is used as the plasmaexcitation gas in the subsequent oxide film formation process, is used,and the removal process of the surface-terminating hydrogen and theoxidation process are conducted in the same processing chambercontinuously.

First, a vacuum vessel (processing chamber) 101 is evacuated and an Argas is introduced first from a shower plate 102. Then, the gas ischanged to the Kr gas. Further, the pressure inside the processingchamber 101 is set to about 13.3 Pa (1 Torr).

Next, a silicon substrate 103 is placed on a stage 104 having a heatingmechanism, and the temperature of a specimen is set to about 400° C. Aslong as the temperature of the silicon substrate 103 is in the range of200-500° C., almost the same results explained as below are obtained. Itshould be noted that the silicon substrate 103 is cleaned by a dilutedhydrofluoric acid in the preprocessing step immediately before and, as aresult, the silicon dangling bonds on the surface are terminated byhydrogen.

Next, a microwave having the frequency of 2.45 GHz is supplied to aradial line slot antenna 106 from a coaxial waveguide 105, wherein themicrowave is introduced into the processing chamber 101 from the radialline slot antenna 106 through a dielectric plate 107 provided on a partof the wall of the processing chamber 101. The introduced microwavecauses excitation of the Kr gas that is introduced into the processingchamber 101 from the shower plate 102 and, consequently, there isinduced high-density Kr plasma right underneath the shower plate 102. Aslong as the frequency of the microwave to be supplied is in the range ofabout 900 MHz or more but not exceeding about 100 GHz, almost the sameresults explained as below are obtained.

In the construction of FIG. 1, the interval between the shower plate 102and the substrate 103 is set to 6cm in this embodiment. The narrower theinterval, the faster the film formation becomes. This embodiment showsthe example of film formation by using the plasma apparatus that usesthe radial line slot antenna, however, it should be noted that theplasma may be induced by introducing the microwave into the processingchamber by other methods.

By exposing the silicon substrate 103 to the plasma thus excited by theKr gas, the surface of the silicon substrate 103 is subjected toirradiation of low energy Kr ions, and the surface-terminating hydrogenare removed.

FIG. 2 shows the result of analysis of the silicon-hydrogen bond on thesurface of the silicon substrate 103 by means of infrared spectrometerand shows the effect of removal of the surface-terminating hydrogen atthe silicon surface by the Kr plasma induced by introducing themicrowave into the processing chamber 101 under the pressure of 13.3 Pa(1 Torr) with the power of 1.2 W/cm².

Referring to FIG. 2, it can be seen that the optical absorption at about2100 cm⁻¹, which is characteristic to the silicon-hydrogen bond, is moreor less vanished after the Kr plasma irradiation conducted for onlyabout 1 second, and is almost completely vanished after irradiation forapproximately thirty seconds. That is, the surface-terminating hydrogenon the silicon surface can be removed by the Kr plasma irradiationconducted for approximately 30 seconds. In this embodiment, thesurface-terminating hydrogen is completely removed by conducting the Krplasma irradiation for 1 minute.

Next, a Kr/O₂ mixed gas is introduced from the shower plate 102 with apartial pressure ratio of 97/3. On this occasion, the pressure of theprocessing chamber is maintained at about 13.3 Pa (1 Torr). In thehigh-density excitation plasma in which the Kr gas and the O₂ gas aremixed, Kr* in the intermediate excitation state and the O₂ moleculescause collision, and it is possible to efficiently form atomic stateoxygen O* in large amount.

In this embodiment, with the atomic state oxygen O* thus formed, thesurface of the silicon substrate 103 is oxidized. In the conventionalthermal oxidation methods conducted on a silicon surface, the oxidationis caused by O₂ molecules or H₂O molecules and a very high processingtemperature of 800° C. or more has been needed. In the oxidationprocessing of the present invention conducted by the atomic stateoxygen, the oxidation is possible at a very low temperature of about400° C. In order to facilitate the collision of Kr* and O₂, it ispreferable that the processing chamber pressure be high. However, underexcessively high pressure, the O* thus formed collide mutually andreturn to O₂ molecules. Obviously, there exists an optimum gas pressure.

FIG. 3 shows the relationship between the thicknesses of the oxide filmformed and the internal pressure of the processing chamber of the casewhere the gas pressure inside the processing chamber 101 is changedwhile maintaining the Kr/O₂ pressure ratio inside the processing chamberto 97/3. In FIG. 3, the temperature of the silicon substrate 103 is setto 400° C. and 10 minutes oxidation processing is conducted.

Referring to FIG. 3, it can be seen that the oxidation rate becomesmaximum when the pressure inside the processing chamber 101 isapproximately 13.3 Pa (1 Torr) and that this pressure or the pressurecondition near this is optimum. This optimum pressure is not limited tothe case where the silicon substrate 103 has the (100) surfaceorientation but is the same also in other cases where the siliconsurface has any other surface orientations.

After the silicon oxide film of the desired film thickness is formed,the introduction of the microwave power is shutdown and the plasmaexcitation is terminated. Further, the Kr/O₂ mixed gas is replaced withthe Ar gas, and the oxidation processing is terminated. It should benoted that the use of the Ar gas before and after this step is intendedto use a gas cheaper than Kr for the purging gas. The Kr gas used in thethis step is recovered and reused.

Following the above oxide film formation, a semiconductor integratedcircuit device including transistors and capacitors is completed afterconducting electrode formation processing, passivation film formationprocessing, hydrogen sintering processing, and the like.

The result of measurement of hydrogen content in the silicon oxide filmformed according to the foregoing processing indicates that the hydrogencontent is about 10¹²/cm² or less in terms of surface density in thecase where the silicon oxide film has a thickness of 3 nm, wherein-itshould be noted that the foregoing measurement was conducted bymeasuring the hydrogen release caused with temperature rise.Particularly, it was confirmed that the oxide film characterized by asmall leakage current shows that the hydrogen content in the siliconoxide film is about 10¹¹/cm² or less in terms of surface density. On theother hand, the oxide film not exposed to the Kr plasma before the oxidefilm formation contained hydrogen with the surface density exceeding10¹²/cm².

Further, the comparison was made between the roughness of the siliconsurface after the oxide film formed according to the foregoingprocessing was removed and the roughness of the silicon surface beforethe oxide film formation wherein the measurement of the surfaceroughness was made by using an atomic force microscope. It was confirmedthat there is caused no change of surface roughness. That is, there iscaused no roughening of silicon surface even when the oxidationprocessing is conducted after the removal of the surface-terminatinghydrogen.

FIG. 4 shows the depth profile of Kr density in the silicon oxide filmformed according to the foregoing processing as measured by the totalreflection X-ray fluorescent spectrometer. It should be noted that FIG.4 shows the result for the silicon (100) surface, however, this resultis not limited to the (100) surface and a similar result is obtainedalso in other surface orientations.

In the experiment of FIG. 4, the partial pressure of oxygen in Kr is setto 3% and the pressure of the processing chamber is set to 13.3 Pa (133Torr). Further, the-plasma oxidation processing is conducted at thesubstrate temperature of 400° C.

Referring to FIG. 4, the Kr density in the silicon oxide film increaseswith increasing distance from the underlying silicon surface and reachesthe value of about 2×10¹¹/cm² at the surface of the silicon oxide film.This indicates that the silicon oxide film obtained according to theforegoing processing is a film in which the Kr concentration is constantin the film in the region where the distance to the underlying siliconsurface is 4 nm or more and in which the Kr concentration decreasestoward the silicon/silicon oxide interface in the region within thedistance of 4 nm from the silicon surface.

FIG. 5 shows the dependence of the leakage current on the appliedelectric field for the silicon oxide film obtained according to theforegoing process. It should be noted that the result of FIG. 5 is forthe case where the thickness of the silicon oxide film is 4.4 nm. Forthe purpose of comparison, FIG. 5 also shows the leakage currentcharacteristic of the oxide film of the same thickness in the case whereno exposure to the Kr plasma was conducted before the formation of theoxide film.

Referring to FIG. 5, the leakage current characteristic of the siliconoxide film not exposed to the Kr plasma is equivalent to the leakagecurrent characteristic of the conventional thermal oxide film. Thismeans that the Kr/O₂ microwave plasma oxidation processing does notimprove the leakage current characteristics of the oxide film thusobtained very much. On the other hand, in the oxide film formedaccording to this embodiment where the oxidation processing is conductedby introducing the Kr/O₂ gas after removing the terminated hydrogen bythe Kr plasma irradiation, it can be seen that the leakage current isimproved by the order of 2 or 3 as compared with the leakage current ofthe silicon oxide film formed by the conventional microwave plasmaoxidation processing when measured at the same electric field,indicating that the silicon oxide film formed by this embodiment hasexcellent low leakage characteristics. It is further confirmed that asimilar improvement of leakage current characteristic is achieved alsoin the silicon oxide film having a much thinner film thickness of up toabout 1.7 nm.

FIG. 6 shows the result of measurement of the leakage currentcharacteristics of the silicon oxide film of this embodiment for thecase where the thickness of the silicon oxide film is varied. In FIG. 6,Δ shows the leakage current characteristic of a conventional thermaloxide film, ◯ shows the leakage current characteristic of the siliconoxide film formed by conducting the oxidation by the Kr/O₂ plasma whileomitting the exposure process to the Kr plasma, and ● shows the leakagecurrent characteristic of the silicon oxide film of this embodiment inwhich the oxidation is conducted by the Kr/O₂ plasma after exposure tothe Kr plasma. In FIG. 6, it should be noted that the data representedby ▪ show the leakage current characteristic of an oxynitride film to beexplained later.

Referring to FIG. 6, it can be seen that the leakage currentcharacteristic of the silicon oxide film represented by ◯ and formed bythe plasma oxidation processing while omitting the exposure process tothe Kr plasma coincides with the leakage current characteristic of thethermal oxide film represented by Δ, while it can be seen also that theleakage current characteristics of the silicon oxide film of thisembodiment and represented by ● is reduced with respect to the leakagecurrent characteristics represented by ◯ by the order of 2-3. Further,it can be seen that a leakage current of 1×10⁻² A/cm², which iscomparable to the leakage current of the thermal oxide film having thethickness of 2 nm, is achieved in the silicon oxide film of thisembodiment even when the thickness thereof is approximately 1.5 nm.

Further, the measurement of the surface orientation dependence conductedon the silicon/silicon oxide interface state density for the siliconoxide film obtained by this embodiment has revealed the fact that a verylow interface state density of approximately 1×10¹⁰ cm⁻²eV⁻¹ is obtainedfor any silicon surface of any surface orientation.

Further, the oxide film formed by this embodiment shows equivalent orsuperior characteristics as compared with the conventional thermal oxidefilm with regard to electric and reliability characteristics, such asbreakdown voltage characteristics, hot carrier resistance, electriccharges QBD (Charge-to-Breakdown) up to the failure of the silicon oxidefilm when a stress current is applied.

As described above, it is possible to form a silicon oxide film on asilicon of any surface orientation even at a low temperature of 400° C.by conducting the silicon oxidation processing by the Kr/O₂ high-densityplasma after removal of the surface-terminating hydrogen. It is thoughtthat such an effect is achieved because of the reduced hydrogen contentin the oxide film caused as a result of the removal of the terminatinghydrogen and because of the fact that the oxide film contains Kr.Because of the reduced amount of hydrogen in the oxide film, it isbelieved that weak element bonding is reduced in the silicon oxide film.Further, because of the incorporation of Kr in the film, the stressinside the film and particularly at the Si/SiO₂ interface is relaxed,and there is caused a reduction of electric charges in the film orinterface state density. Consequently, the electric properties of thesilicon oxide film is significantly improved.

Particularly, it is believed that reducing the hydrogen concentration tothe level of 10¹²/cm² or less, preferably to the level of 10¹¹ cm² orless, and incorporation of Kr with a concentration of about 5×10¹¹/cm²or less in terms of the surface concentration are thought to contributeto the improvement of electric properties and reliabilitycharacteristics of the silicon oxide film.

In order to realize the oxide film of the present invention, in additionto the apparatus of FIG. 1, it is also possible to use a plasmaprocessing apparatus capable of conducting the oxide film formation atlow temperatures by using plasma. For example, it is also possible touse a two-stage shower plate-type plasma processing apparatus that isprovided with a first gas release structure releasing the Kr gas forplasma excitation by a microwave and a second gas release structure thatis different from the first gas release structure and releases theoxygen gas.

In this embodiment, it should be noted that the oxidation processing isterminated such that the feeding of the microwave power is shutdown andplasma excitation is finished upon formation of the silicon oxide filmto a desired film thickness, followed by the process of replacing theKr/O₂ mixed gas with the Ar gas. However, it is also possible tointroduce a Kr/NH₃ mixed gas from the shower plate 102 with the partialpressure ratio of 98/2 before shutting down the microwave power whilemaintaining the pressure at about 13.3 Pa (1 Torr), and terminate theprocessing when a silicon nitride film of approximately 0.7 nm is formedon the surface of the silicon oxide film. According to such a method, asilicon oxynitride film in which a silicon nitride film is formed on thesurface thereof is obtained, and thus it becomes possible to form aninsulation film having a higher specific dielectric constant.

Second Embodiment

Next, a description will be given of nitride film formation at lowtemperatures by using plasma. An apparatus similar to that shown in FIG.1 is used for the nitride film formation.

In this embodiment, it is preferable to use Ar or Kr for the plasmaexcitation gas for removing the terminating hydrogen and for the nitridefilm formation, in order to form a high-quality nitride film.

Hereinafter, an example of using Ar will be represented.

First, the interior of the vacuum vessel (processing chamber) 101 isevacuated to vacuum and an Ar gas is introduced from the shower plate102 such that the pressure inside the processing chamber is set to about13.3 Pa (100 mTorr).

Next, the silicon substrate 103, subjected to hydrogenated watercleaning and the silicon dangling bonds at the surface are terminated byhydrogen in the preprocessing step immediately before, is introducedinto the processing chamber 101 and is placed on the stage 104 havingthe heating mechanism. Further, the temperature of the specimen is setto 500° C. As long as the temperature is in the range of 300-550° C.,results almost the same as the one described below are obtained.

Next, a microwave of 2.45 GHz is supplied into the processing chamberfrom the coaxial waveguide 105 via the radial line slot antenna 106 andthe dielectric plate 107 and a high-density plasma of Ar is generated inthe processing chamber. As long as the frequency of the suppliedmicrowave is in the range of about 900 MHz or more but not exceedingabout 10 GHz, results almost the same as the one described below areobtained. The interval between the shower plate 102 and the substrate103 is set to 6 cm in this embodiment. With decreasing interval, fasterdeposition rate becomes possible. While this embodiment shows theexample of film formation by a plasma apparatus that uses the radialline slot antenna, it is also possible to introduce the microwave intothe processing chamber by other methods.

The silicon surface thus exposed to the plasma excited based on an Argas is subjected to bombardment of low energy Ar ions, and thesurface-terminating hydrogen are removed. In this embodiment, the Arplasma exposure is conducted for 1 minute.

Next, an NH₃ gas is introduced and mixed to the Ar gas from the showerplate 102 with a partial pressure ratio of 2%. On this occasion, thepressure of the processing chamber is held at about 13.3 Pa (100 mTorr).In excited high-density plasma in which the Ar gas and the NH₃ gas aremixed, there are caused collision of Ar* in the intermediate excitedstate and the NH₃ molecules, and NH* radicals are formed efficiently.The NH* radicals cause nitridation of the silicon substrate surface.

Upon formation of the silicon nitride film with a desired thickness, theintroduction of the microwave power is shutdown and the excitation ofthe plasma is terminated. Further, the Ar/NH₃ mixed gas is replaced withthe Ar gas and the nitridation processing is terminated.

Further, following the above nitride film formation, electrode formationprocesses, passivation film formation processes, hydrogen sinteringprocesses, and the like are conducted, and a semiconductor integrateddevice that includes transistors and capacitors is completed.

While this embodiment showed the example in which the nitride film isformed by the plasma apparatus that uses the radial line slot antenna,it is also possible to introduce the microwave into the processingchamber by other methods. In addition, while this embodiment uses Ar forthe plasma excitation gas, similar results are obtained also when Kr isused. Further, while this embodiment uses NH₃ for the plasma processgas, it is also possible to use a mixed gas of N₂ and H₂ for thispurpose.

In the silicon nitride film formation process of the present invention,it is one of important requirements that there remains hydrogen in theplasma even after the surface-terminating hydrogen are removed. As aresult of existence of hydrogen in the plasma, the dangling bonds insidethe silicon nitride film as well as the dangling bond at the interfaceare terminated by forming Si—H bonds or N—H bond. Consequently, electrontraps are eliminated from the silicon nitride film and the interface.

The existence of the Si—H bond and the N—H bond in the nitride film ofthe present invention is confirmed respectively by infrared absorptionspectroscopy and by X-ray photoelectron spectroscopy. As a result ofexistence of hydrogen, the hysteresis in the CV characteristics iseliminated and the interface state density at the silicon/siliconnitride film is suppressed to 2×10¹⁰ cm⁻². In the case of forming thesilicon nitride film by using a rare gas (Ar or Kr) and an N₂/H₂ mixedgas, it is possible to suppress the traps of electrons or holes in thefilm drastically by setting the partial pressure of the hydrogen gas to0.5% or more.

FIG. 7 shows the pressure dependence of the silicon nitride filmthickness formed according to the process described above. In theexperiment of FIG. 7, it should be noted that the Ar/NH₃ partialpressure ratio was set to 98/2 and the deposition time was 30 minutes.

Referring to FIG. 7, it can be seen that there occurs an increase ofdeposition rate of the nitride film by reducing the pressure in theprocessing chamber and thus by increasing the energy given to NH₃ (orN₂/H₂) by the rare gas (Ar or Kr) From the viewpoint of efficiency ofnitride film formation, it is preferable that the gas pressure be in therange of 6.65-13.3 Pa (50-100 mTorr). However, from the viewpoint ofproductivity, it is preferable to use a unified pressure suitable to theoxidation, for example, 133 Pa (1 Torr), also for nitridation, in theprocess where oxidation and nitridation are continuously conducted, aswill be explained in other embodiments. Additionally, it is preferablethat the partial pressure of NH₃ (or N₂/H₂) in the rare gas be in therange of 1-10%, more preferably, in the range of 2-6%.

It should be noted that the silicon nitride film obtained by thisembodiment showed the specific dielectric constant of 7.9, which valueis about twice as large as the specific dielectric constant of a siliconoxide film.

Measurement of the current versus voltage characteristics of the siliconnitride film obtained by this embodiment has revealed the fact that aleakage current characteristic smaller by the order of 5-6 than that ofa thermal oxide film having the thickness of 1.5 nm is obtained in thecase where the film thickness is 3.0 nm (equivalent to the oxide filmthickness of 1.5 nm), under the condition that a voltage of 1V isapplied. This means that it is possible to break through the limitationof miniaturization that appears in the transistors using a silicon oxidefilm for the gate insulation film, by using the silicon nitride film ofthis embodiment.

It should be noted that the film formation condition of the nitride filmdescribed above as well as the physical and electrical properties arenot limited on the (100) oriented silicon surface but are valid in thesame way on the silicon of any surface orientation including the (111)surface.

It is believed that the preferable results achieved by this embodimentare not only attained by the removal of the terminating hydrogen, butalso by the existence of Ar or Kr in the nitride film. In other words,in the nitride film of this embodiment, it is believed that Ar or Krexisting in the nitride film relaxes the stress inside the nitride filmor at the silicon/nitride film interface, and as a result, the fixedelectric charges in the silicon nitride film or the interface statedensity is reduced, thereby significantly improving the electricproperties and the reliability characteristics.

Particularly, it is thought that the existence of Ar or Kr with thesurface density of 5×10¹¹/cm² or less contributes to the improvement ofthe electric properties and reliability characteristics of the siliconnitride film, as in the case of the silicon oxide film.

In order to realize the nitride film of the present invention, inaddition to the apparatus of FIG. 1, it is also possible to use anotherplasma processing apparatus capable of conducting oxide film formationat low temperatures by using plasma. For example, it is also possible toconduct film formation by using a two-stage shower plate type plasmaprocessing apparatus that includes a first gas release structurereleasing an Ar or Kr gas for excitation of plasma by microwave and asecond gas release structure that is different from the first gasrelease structure and releases the NH₃ (or N₂/H₂) gas.

Third Embodiment

Next, a description will be given of an embodiment that uses, for thegate insulation film, a two-layer structure of an oxide film and nitridefilm formed at a low-temperature by using plasma.

The formation apparatus of the oxide film and the nitride film used inthis embodiment is identical with that of FIG. 1. In this embodiment, Kris used for the plasma excitation gas for formation of the oxide filmand the nitride film.

First, the vacuum vessel (processing chamber) 101 is evacuated to vacuumand an Ar gas is introduced into the processing chamber 101 from theshower plate 102. Then, the gas to be introduced the next is switched tothe Kr gas from the initial Ar gas, and the pressure of the processingchamber 101 is set to about 133 Pa (1 Torr).

Next, the silicon substrate 103, subjected to diluted hydrofluoric acidtreatment and the surface dangling bonds of silicon are terminated byhydrogen in the preprocessing step immediately before, is introducedinto the processing chamber 101 and placed on the stage 104 having theheating mechanism. Further, the temperature of the specimen is set to400° C.

Next, a microwave having the frequency of 2.45 GHz is supplied to theradial line slot antenna 106 from the coaxial waveguide 105 for 1minute, wherein the microwave is introduced into the processing chamber101 via the dielectric plate 107. The surface-terminating hydrogen isremoved by exposing the surface of the silicon substrate 103 to thehigh-density Kr plasma thus generated in the processing chamber 101.

Next, the pressure of the processing chamber 101 is maintained at 133 Pa(1 Torr) and a Kr/O₂ mixed gas is introduced from the shower plate 102with the partial pressure ratio of 97/3. Thereby, there is formed asilicon oxide film on the surface of the silicon substrate 103 with athickness of 1.5 nm.

Next, the supply of the microwave is shutdown momentarily andintroduction of the O₂ gas is terminated. After purging the interior-ofthe vacuum vessel (processing chamber) 101 with Kr, a mixed gas ofKr/NH₃ is introduced from the shower plate 102 with a partial pressureratio of 98/2. Further, the microwave having the frequency of 2.56 GHzis supplied again with the pressure of the processing chamber set toabout 133 Pa (1 Torr), so as to generate the high-density plasma in theprocessing chamber 101, thereby forming a silicon nitride film on thesurface of the silicon oxide film with the thickness of 1 nm.

Upon formation of the silicon nitride film with the desired thickness,the introduction of the microwave power is stopped and the plasmaexcitation is terminated. Further, the Kr/NH₃ mixed gas is replaced withthe Ar gas and the oxynitridation processing is terminated.

Following the oxynitride film formation described above, by conductingelectrode formation processing, passivation film formation processing,hydrogen sintering processing, and the like, a semiconductor integratedcircuit device having transistors or capacitors is completed.

Measurement of the effective dielectric constant conducted on alaminated gate insulation film thus formed has revealed the value ofapproximately 6. Also, electric properties and reliabilitycharacteristics, such as leakage current characteristic, breakdownvoltage characteristic, and hot-carrier resistance, were excellent as inthe case of the first embodiment. The gate insulation film thus obtainedshowed no dependence on the surface orientation of the silicon substrate103, and the gate insulation film having excellent characteristics wasformed also on the silicon of any surface orientation other than the(100) surface. In this manner, the gate insulation film having both thelow interface state properties of the oxide film and the high dielectricconstant characteristics of the nitride film was realized.

This embodiment explained the two-layer construction of an oxide filmand a nitride film, where the oxide film is located closer to thesilicon side. However, it is also possible to change the order of theoxide film and the nitride film according to the proposes. In addition,it is also possible to form a laminated film having more number offilms, such as oxide film/nitride film/oxide film, nitride film/oxidefilm/nitride film, and the like.

Fourth Embodiment

Next, a description will be given of an embodiment that uses anoxynitride film formed at low temperature by using plasma for the gateinsulation film.

It should be noted that the oxynitride film formation apparatus used inthis embodiment is identical with that of FIG. 1. In this embodiment, Kris used for the plasma excitation gas.

First, the interior of the vacuum vessel (processing camber) 101 isevacuated to vacuum, and an Ar gas is introduced into the processingchamber 101 from the shower plate 102. Next, the gas introduced to theprocessing chamber 101 is switched to a Kr gas from the Ar gas, and thepressure inside the processing chamber is set to about 133 Pa(1 Torr).

In addition, the silicon substrate 103, subjected to dilutedhydrofluoric acid cleaning and the silicon dangling bonds at the surfaceare terminated by hydrogen in the preprocessing step immediately before,is introduced into the processing chamber 101 and is placed on the stage104 having the heating mechanism. Further, the temperature of thespecimen is set to 400° C.

Next, a microwave having the frequency of 2.45 GHz is supplied to theradial line slot antenna 106 from the coaxial waveguide 105 for 1minute, wherein the microwave is introduced into the processing chamber107 from the radial lien slot antenna 106 through the dielectric plate107. Thereby, there is generated high-density plasma of Kr in theprocessing chamber 101. The surface-terminating hydrogen is removed byexposing the surface of the silicon substrate 103 to the plasma thusexcited by the Kr gas.

Next, the pressure of the processing chamber 101 is maintained at about133 Pa (1 Torr) and a mixed gas of Kr/O₂/NH₃ is introduced from theshower plate 102 with the partial pressure ratio of 96.5/3/0.5. Thereby,a silicon oxynitride film of 3.5 nm is formed on the silicon surface.Upon formation of the silicon oxynitride film of the desire filmthickness, the introduction of the microwave power is shutdown and theplasma excitation is terminated. Further, the Kr/O₂/NH₃ mixed gas isreplaced with the Ar gas and the oxynitridation processing isterminated.

Following the oxide film formation described above, by conductingelectrode formation processing, passivation film formation processes,hydrogen sintering processes, and the like, a semiconductor integratedcircuit device having transistors or capacitors is completed.

As shown in FIG. 8, the formation density of the atomic state oxygen O*as measured by the photoemission analysis does not change substantiallywhen the mixing ratio of the Kr/O₂/NH₃ gas is in the range of97/3/0-95/3/2. However, when the ratio of NH₃ is increased further, theamount of formation of the atomic state oxygen O* is reduced and theamount of the atomic state hydrogen is increased. Particularly, in thecase where the mixing ratio of the Kr/O₂/NH₃ gas is about 96.5/3/0.5,the leakage current becomes minimum and the withstand voltage and theresistance against electric charge injection are improved.

FIG. 9 shows the concentration distribution of silicon, oxygen, andnitrogen in the oxynitride film of the this embodiment as measured by asecondary ion mass spectrometer. It should be noted that, in FIG. 9, thehorizontal axis represents the depth as measured from the surface of theoxynitride film. In FIG. 9, it can be seen that the distribution ofsilicon, oxygen, and nitrogen is changing gently in the film. However,this is caused by non-uniformity of etching and does not mean that thefilm thickness of the oxynitride film is uneven.

Referring to FIG. 9, it can be seen that the concentration of nitrogenin the oxynitride film is high at the silicon/silicon oxynitride filminterface and at the silicon oxynitride film surface, and decreases atthe central part of the oxynitride film. The amount of nitrogenincorporated into the oxynitride film is several ten percent or less ascompared with silicon or oxygen.

FIG. 10 shows the dependence of leakage current of the oxynitride filmof the this embodiment on the applied electric field. It should be notedthat, however, FIG. 10 also shows the leakage current characteristic ofthe oxide film of the same film thickness in which the exposure processto the Kr plasma is not conducted before the oxide film formation by themicrowave plasma and the leakage current characteristic of the oxidefilm formed by a thermal oxidation process for the purpose ofcomparison.

Referring to FIG. 10, it can be seen that, as compared with the oxidefilm formed by the conventional technique, the value of the leakagecurrent at the same electric field is reduced by the order of 2-4 in theoxynitride film of the this embodiment in which the oxynitridationprocessing is conducted by introducing the Kr/O₂/NH₃ gas after removingthe terminating hydrogen by the Kr plasma irradiation and that excellentlow-leakage characteristics are obtained.

It should be noted that, in FIG. 6 explained before, the relationshipbetween the leakage current characteristic and the film thickness of theoxynitride film thus formed is represented by ▪.

Referring to FIG. 6 again, it can be seen that the oxynitride filmformed by this embodiment after conducting the Kr irradiation has asimilar leakage characteristic to the oxide film formed with a similarprocess and, particularly, the leakage current is only 1×10⁻² A/cm² alsoin the case where the film thickness is approximately 1.6 nm.

It should be noted that the oxynitride film of this embodiment alsoshowed excellent electric properties and reliability characteristics,such as breakdown voltage characteristic and hot carrier resistance,superior to the oxide film of the first embodiment described above.Further, there was observed no dependence on the surface orientation ofthe silicon substrate, and thus, it is possible to form a gateinsulation film of excellent characteristic not only on the (100)surface of silicon but also on the silicon surface of any surfaceorientation.

As described above, it is possible to form a silicon oxynitride film ofexcellent characteristics and film quality on the silicon surface of anysurface orientation even at the low temperature of 400° C. by conductingthe silicon oxynitridation processing by using the Kr/O₂/NH₃high-density plasma, after removing the surface-terminating hydrogen.

The reason why such preferable effect can be achieved by this embodimentis attributed not only to the reduction of hydrogen content in theoxynitride film caused by removal of the surface-terminating hydrogen,but also to the nitrogen contained in the oxynitride film with aproportion of several ten percent or less. In the oxynitride film ofthis embodiment, the content of Kr is approximately 1/10 or less ascompared with the oxide film of the first embodiment, and in place ofKr, a large amount of nitrogen is contained. That is, in thisembodiment, it is believed that the reduction of hydrogen in theoxynitride film causes reduction of weak bonds in the silicon oxynitridefilm, the existence of nitrogen causes relaxation of stress in the filmor at the Si/SiO₂ interface, and consequently, trapped electricalcharges in the film or the surface state density is reduced, and theelectric properties of the oxynitride film is improved significantly.Particularly, it is believed the reduction of hydrogen concentration inthe oxynitride film to 10²² cm⁻² or less, more preferably, 10¹¹ cm⁻² orless, and the existence of nitrogen in the film with a proportion ofseveral ten percent with respect to silicon or oxygen contribute to theimprovement of the electric properties and reliability characteristicsof the silicon oxynitride film.

In this embodiment, the oxynitridation processing is terminated suchthat the introduction of the microwave power is shutdown at the end ofthe oxynitridation processing upon formation of the silicon oxynitridefilm with the desired thickness, and the Kr/O₂/NH₃ mixed gas is replacedwith the Ar gas. On the other hand, it is also possible to terminate theoxynitridation processing by introducing a Kr/NH₃ mixed gas with thepartial pressure ratio of 98/2 from the shower plate 102 before theshutdown of the microwave power while maintaining the pressure at about133 Pa (1 Torr) and form a silicon nitride film on the surface of thesilicon oxynitride film with the thickness of approximately 0.7 nm.According to this method, a silicon nitride film is formed on thesurface of the silicon oxynitride film and an insulation film having ahigher dielectric constant can be formed.

Fifth Embodiment

Next, a description will be given of a fabrication method of asemiconductor device according to a fifth embodiment of the presentinvention in which semiconductor device a high-quality silicon oxidefilm formed on a corner part of the device isolation sidewall thatconstitutes a shallow-trench isolation or on a silicon surface having asurface form with projections and depressions.

FIG. 11A shows a conceptual diagram of shallow trench isolation.

Referring to FIG. 11A, the illustrated shallow trench isolation isformed by forming an isolation trench on a surface of a siliconsubstrate 1003 by conducting a plasma etching, filling the trench thusformed with a silicon oxide film 1002 formed by a CVD method, andplanarizing the silicon oxide film 1002 by a CMP method, and the like.

In this embodiment, the silicon substrate is exposed to an oxidizingatmosphere at 800-900° C. after the polishing step of the silicon oxidefilm 1002 according to the CMP method to conduct sacrifice oxidation,and the silicon oxide film formed by the sacrifice oxidation is etchedaway in a chemical solution containing hydrofluoric acid. Thereby, asilicon surface terminated with hydrogen is obtained. In thisembodiment, the surface-terminating hydrogen is removed by using the Krplasma with a procedure similar to the one in the first embodiment.Thereafter, the Kr/O₂ gas is introduced and the silicon oxide film isformed with the thickness of approximately 2.5 nm.

According to this embodiment, as shown in FIG. 11C, the silicon oxidefilm is formed with a uniform thickness even on the corner part of theshallow trench isolation without causing decrease of silicon oxide filmthickness. The silicon oxide film formed by the plasma oxidation methodusing the Kr plasma has excellent QBD (Charge to Breakdown)characteristics including the shallow trench isolation part, and thereis caused no increase of leakage current even in the case where theamount of the injected electric charges are 10² C/cm². Thus, thereliability of the device is improved significantly.

In the case of forming the silicon oxide film by the conventionalthermal oxidation method, as shown in FIG. 11B, the thinning of the filmbecomes severe at the corner part of the shallow trench isolation withincreasing taper angle of the shallow trench isolation. However, in thecase of the plasma oxidation of the present invention, no such thinningof the silicon oxide film is caused at the corner part of the shallowtrench isolation even when the taper angle is increased. Thus, in thisembodiment, by making the taper angle for the trench near the rightangle in the shallow trench isolation structure, it is possible toreduce the area of the device isolation region and further increaseintegration density in the semiconductor device. The taper angle ofabout 70 degrees has been used for the device isolation part in theconventional thermal oxidation technology, because of the limitationcaused by the thinning of the thermal oxide film at the trench cornerpart as shown in FIG. 11B. According to the present invention, however,it is possible to use the angle of 90 degrees.

FIG. 12 shows the cross-sectional view of the silicon oxide film formedon a silicon substrate having an undulating surface form formed byconducting a 90-degree etching on the silicon substrate, with athickness of 3 nm according to the procedure of the first embodiment.

Referring to FIG. 12, it can be confirmed that a silicon oxide film ofuniform thickness is formed on any of the surfaces.

The oxide film formed as described above has good electric propertiessuch as leakage current or breakdown voltage. Thus, the presentinvention can realize a high-density semiconductor integrated devicehaving a silicon three-dimensional structure that includes pluralsurface orientations such as a vertical structure.

Sixth Embodiment

Next, a description will be given of a flash memory device according toa sixth embodiment of the present invention that uses the formationtechnology of oxide film and nitride film or that of oxynitride film atlow temperature by using plasma. In the description below, it should benoted that the explanation is made by taking a flash memory device as anexample, however, the present invention is applicable also to EPROMs,EEPROMs, and the like.

FIG. 13 shows the schematic cross-sectional view of a flash memorydevice according to this embodiment.

Referring to FIG. 13, the flash memory device is constructed on asilicon substrate 1201 and includes a tunneling oxide film 1202 formedon the silicon substrate 1201, a first polysilicon gate electrode 1203formed on the tunneling oxide film 1202 as a floating gate electrode, asilicon oxide film 1204 and a silicon nitride film 1205 formedconsecutively on the polysilicon gate electrode 1203, and a secondpolysilicon gate electrode 1206 formed on the silicon nitride film 1205as a control gate electrode. In FIG. 13, illustration of the sourceregion, drain region, contact hole, wiring patterns, and the like, isomitted. It should be noted that the silicon oxide film 1202 is formedby the silicon oxide film formation method explained in the firstembodiment, and the laminated structure of the silicon oxide film 1204and the nitride film 1205 is formed by the formation method of siliconnitride film explained in the third embodiment.

FIGS. 14-17 are schematic cross-sectional views for explaining thefabrication method of the flash memory device of this embodiment step bystep.

Referring to FIG. 14, a silicon substrate 1301 includes a flash memorycell region A, a high-voltage transistor region B, and a low-voltagetransistor region C that are defined by a field oxide film 1302, whereina silicon oxide film 1303 is formed on the surface of the siliconsubstrate 301 in each of the regions A-C. The field oxide film 1302 maybe formed by a selective oxidation process (LOCOS method) or shallowtrench isolation method.

In this embodiment, Kr is used as the plasma excitation gas for theremoval of the surface-terminating hydrogen or for the formation of theoxide film and the nitride film. The oxide film and nitride filmformation apparatus is identical with that of FIG. 1.

Next, in the step of FIG. 15, the silicon oxide film 1303 is removedfrom the memory cell region A, and the silicon surface is terminated byhydrogen by diluted hydrofluoric acid cleaning. Further, a tunnelingoxide film 1304 is formed similarly to the first embodiment describedabove.

That is, as in the above-described first embodiment, the vacuum vessel(processing chamber) 101 is evacuated to vacuum and the Ar gas isintroduced into the processing chamber 101 from the shower plate 102.Next, the Ar gas is switched to the Kr gas and the pressure in theprocessing chamber 101 is set to about 1 Torr.

Next, the silicon oxide film 1303 is removed and the silicon substratesubjected to the diluted hydrofluoric acid treatment is introduced intothe processing chamber 101 as the silicon substrate 103 of FIG. 1 and isplaced on the stage 104 having the heating mechanism. Further, thetemperature of the substrate is set to 400° C.

Further, a microwave having the frequency of 2.45 GHz is supplied fromthe coaxial waveguide 105 to the radial line slot antenna 106 for 1minute, wherein the microwave is introduced into the processing chamber101 from the radial line slot antenna 106 through the dielectric plate107. By exposing the surface of the silicon substrate 1301 to thehigh-density Kr plasma thus formed in the processing chamber 101, theterminating hydrogen are removed from the silicon surface of thesubstrate 1301.

Then, the Kr gas and the O₂ gas are introduced from the shower plate102, and the silicon oxide film 1304 used for the tunneling insulationfilm is formed on the region A with a thickness of 3.5 nm. Subsequently,a first polysilicon layer 1305 is deposited so as to cover the siliconoxide film 1304.

Next, the first polysilicon layer 1305 is removed from the high voltageand low voltage transistor formation regions B and C, respectively, by apatterning process, such that the first polysilicon pattern 1305 is leftonly on the tunneling oxide film 1304 in the memory cell region A.

After this etching, cleaning is conducted and the surface of thepolysilicon pattern 1305 is terminated with hydrogen.

Next, in the step of FIG. 16, as in the third embodiment describedabove, an insulation film 1306 having an ON structure of a lower oxidefilm 1306A and an upper nitride film 1306B is formed so as to cover thesurface of the polysilicon pattern 1305 similarly to the thirdembodiment.

The ON film is formed as follows.

The vacuum vessel (processing chamber) 101 is evacuated to vacuum andthe Ar gas introduced from the shower plate 102 is switched to the Krgas. In addition, the pressure inside the processing chamber is set toabout 133 Pa (1 Torr). Next, the silicon substrate 1301 carrying thepolysilicon pattern 1305 in the state that the hydrogen termination ismade is introduced into the processing chamber 101 and is placed on thestage 104 having the heating mechanism. Further, the temperature of thespecimen is set to 400° C.

Next, a microwave having the frequency of 2.45 GHz is supplied to theradial line slot antenna 106 from the coaxial waveguide 105 for about 1minute, wherein the microwave is introduced into the processing chamber101 from the radial line slot antenna 106 through the dielectric plate107, and there is generated a high-density Kr plasma. As a result, thesurface of the polysilicon pattern 1305 is exposed to the Kr gas and thesurface terminating hydrogen is removed.

Next, a Kr/O₂ mixed gas is introduced into the processing chamber 101from the shower plate 102 while maintaining the pressure inside theprocessing chamber 101 to about 133 Pa (1 Torr), and a silicon oxidefilm is formed on the polysilicon surface with a thickness of 3 nm.

Next, after the supply of the microwave is shutdown temporarily, theintroduction of the Kr gas and the O₂ gas is interrupted. The interiorof the vacuum vessel (processing chamber) 101 is evacuated, and the Krgas and an NH₃ gas are introduced from the shower plate 102. Thepressure inside the processing chamber 101 is set to about 13.3 Pa (100mTorr) and the microwave of 2.45 GHz is supplied again into theprocessing chamber 101 via the radial line slot antenna 106. Thereby,high-density plasma is generated in the processing chamber and a siliconnitride film is formed on the silicon oxide film surface with thethickness of 6 nm.

When an ON film with a thickness of 9 nm was formed as described above,the film thickness of the ON film thus obtained was uniform, and nodependence on the polysilicon surface orientation was observed. Thus, itwas realized that the extremely uniform film could be obtained.

After such a process of formation of the ON film, the insulation film1306 is removed from the high-voltage and low-voltage transistor regionsB and C, respectively, by patterning in the step of FIG. 17, and then,ion implantation for threshold voltage control is conducted on thehigh-voltage and low-voltage transistor regions B and C, respectively.Further, the oxide film 1303 formed on the regions B and C is removed,and a gate oxide film 1307 is formed on the region B with a thickness of5 nm. Thereafter, a gate oxide film 1308 is formed on the region C witha thickness of 3 nm.

Then, a second polysilicon layer 1309 and a silicide layer 1310 areformed consecutively on the entire structure including the field oxidefilm 1302. In addition, gate electrodes 1311B and 1311C are formed inthe high-voltage transistor region B and the low-voltage transistorregion C, respectively, by patterning the second polysilicon layer 1309and the silicide layer 1310. Further, a gate electrode 1311A is formedin correspondence to the memory cell region A.

After the step of FIG. 17, source and drain regions are formed accordingto a standard semiconductor process, and the device is completed byconducting formation of interlayer insulation films and contact holesand formation of wiring patterns.

In the present invention, it should be noted that the insulation films1306A and 1306B maintain good electric properties even when thethickness thereof is reduced to about one half the conventionalthickness of the oxide film or nitride film. In other words, thesesilicon oxide film 1306A and silicon nitride film 1306B maintain goodelectric properties even when the thickness thereof is reduced, aredense, and have high quality. Further, it should be noted that, becausethe silicon oxide film 1306A and the silicon nitride film 1306B areformed at low temperature, there occurs no thermal budget or the like atthe interface between the gate polysilicon and the oxide film, and goodinterface is obtained.

The flash memory device of the present invention can perform writing anderasing operations of information at low voltage and suppress thegeneration of substrate current. Thereby, deterioration of the tunnelinginsulation film is suppressed. Hence,-a non-volatile semiconductormemory in which the flash memory devices of the present invention arearranged in a two-dimensional array can be produced with high yield andshows stable characteristics.

In the flash memory device of the present invention, the leakage currentis small due to the excellent film quality of the insulation films 1306Aand 1306B. Also, it is possible to reduce the film thickness withoutincreasing the leakage current. Thus, it becomes possible to perform thewriting or erasing operation at an operational voltage of about 5V. As aresult, the memory retention time of the flash memory device isincreased by the order of 2 or more as compared with the conventionalone, and the number of times of possible rewriting operation isincreased by the order of 2 or more.

It should be noted that the film structure of the insulation film 1306is not limited to the ON structure explained above, but it is alsopossible to use an O structure formed of an oxide film similar to thatof the first embodiment, an N structure formed of a nitride film similarto that of the second embodiment, or an oxynitride film similar to theone in the fourth embodiment. Further, the insulation film 1306 may havean NO structure formed of a nitride film and an oxide film, an ONOstructure in which an oxide film, a nitride film, and an oxide film arelaminated consecutively, or an NONO structure in which a nitride film,an oxide film, a nitride film, and an oxide film are laminatedconsecutively. Choice of any of the foregoing structures can be madeaccording to the purpose from the viewpoint of compatibility with thegate insulation film in the high voltage transistor or low voltagetransistor in the peripheral circuit or from the viewpoint ofpossibility of shared use.

Seventh Embodiment

It should be noted that the formation of the gate insulation film byusing the foregoing Kr/O₂ microwave-excited high-density plasma or theformation of the gate nitride film by using the Ar (or Kr)/NH₃ (orN₂/H₂) microwave-excited high-density plasma by using the apparatus ofFIG. 1 is applicable to the formation of a semiconductor integratedcircuit device on a silicon-on-insulator (metal-substrate SOI) waferincluding a metal layer in the underlying silicon in whichmetal-substrate SOI conventional high temperature process is notpossible. Particularly, the effect of removal of the terminatinghydrogen appears conspicuously in the SOI structure having a smallsilicon film thickness and performing completely depleted operation.

FIG. 18 shows a cross-sectional view of a MOS transistor having ametal-substrate SOI structure.

Referring to FIG. 18, 1701 is a low-resistance semiconductor layer ofn⁺-type or p⁺-type, 1702 is a silicide layer of such as NiSi, 1703 is aconductive nitride layer such as TaN or TiN, 1704 is a metal layer ofsuch as Cu, 1705 is a conductive nitride layer of such as TaN or TiN,1706 is a low-resistance semiconductor layer of n⁺-type or p⁺-type, 1707is a nitride insulation film such as AlN, Si₃N₄, and the like, 1708 isan SiO₂ film, 1709 is an SiO₂ layer or a BPSG layer or an insulationlayer combining these, 1710 is a drain region of n⁺-type, 1711 is asource region of n⁺-type, 1712 is a drain region of p⁺-type, 1713 is asource region of p⁺-type, 1714 and 1715 are silicon semiconductor layersoriented in the <111> direction, 1716 is an SiO₂ film formed by theKr/O₂ microwave-excited high-density plasma after removing thesurface-terminating hydrogen by Kr plasma irradiation according to theprocedure of the first embodiment of the present invention, 1717 and1718 are respectively the gate electrodes of an n-MOS transistor and ap-MOS transistor and formed of Ta, Ti, TaN/Ta, TiN/Ti, and the like,1719 is a source electrode of the n-MOS transistor, and 1720 is a drainelectrode of the n-MOS transistor and a p-MOS transistor. Further, 1721is a source electrode of a p-MOS transistor and 1722 is a substratesurface electrode.

In such a substrate including a Cu layer and protected by TaN or TiN,the temperature of thermal processing has to be about 700° C. or lessfor suppressing diffusion of Cu. The source or drain region of n⁺-typeor p⁺-type is formed by conducting the thermal processing at 550° C.after ion implantation of As⁺, AsF₂ ⁺; or BF₂ ⁺.

In the semiconductor device having the device structure of FIG. 18, itshould be noted that the comparison of the transistor sub-thresholdcharacteristics between the case where a thermal oxide film is used forthe gate insulation film and the case where the gate insulation film isformed by the Kr/O₂ microwave-excited high-density plasma processingafter removing the surface-terminating hydrogen by the Kr plasmairradiation, has revealed the fact that there appears kink or leakage inthe sub-threshold characteristics when the gate insulation film isformed by the thermal oxidation, while in the case where the gateinsulation film is formed by the present invention, excellentsub-threshold characteristics are obtained.

When a mesa-type device isolation structure is used, it should be notedthat there appears a silicon surface having a surface orientationdifferent from that of the silicon flat surface part, at the sidewallpart of the mesa device isolation structure. By forming the gateinsulation film by the plasma oxidation using Kr, the oxidation of themesa device isolation sidewall is achieved generally uniformly similarlyto the flat surface part, and excellent electric properties and highreliability are obtained.

Further, it is possible to produce a metal-substrate SOI integratedcircuit device having excellent electric properties and high reliabilityalso in the case of using a silicon nitride film formed by Ar/NH₃according to the procedure of the second embodiment for the gateinsulation film.

In this embodiment, too, it is possible to obtain good electricproperties even in the case where the thickness of the silicon nitridefilm is set to 3 nm (equivalent to the oxide film thickness of 1.5 nm),and the transistor drivability is improved by about twice as comparedwith the case where a silicon oxide film of 3 nm thickness is used.

Eighth Embodiment

FIG. 19 shows a conceptual diagram illustrating an example of thefabrication apparatus according to an eighth embodiment of the presentinvention intended to conduct oxidation processing, nitridationprocessing, or oxynitridation processing on a polysilicon or amorphoussilicon layer formed on a large rectangular substrate such as a glasssubstrate or a plastic substrate on which liquid crystal display devicesor organic electro-luminescence devices are formed.

Referring to FIG. 19, a vacuum vessel (processing chamber) 1807 isevacuated to a low pressure state and a Kr/O₂ mixed gas is introducedfrom a shower plate 1801 provided in the processing chamber 1807.Further, the processing chamber 1807 is evacuated by a lead screw pump1802 such that the pressure inside the processing chamber 1807 is set to133 Pa (1 Torr). Further, a glass substrate 1803 is placed on a stage1804 having a heating mechanism, and the temperature of the glasssubstrate is set to 300° C.

The processing chamber 1807 is provided with a large number ofrectangular waveguides 1805 and a microwave is introduced into theprocessing chamber 1807 from respective slits of the large number ofrectangular waveguides 1805 described above via a dielectric plate 1806,and high-density plasma is generated in the processing chamber 1807. Onthis occasion, the shower plate 1801 provided in the processing chamber1807 functions also as a waveguide for propagating the microwave emittedby the waveguide in the right and left directions in the form of asurface wave.

FIG. 20 shows an example where a polysilicon thin film transistor (TFT),used for driving a liquid crystal display device or an organic ELphotoemission device or for use in a processing circuit, is formed byforming the gate oxide film or gate nitride film of the presentinvention by using the apparatus of FIG. 19.

First, the example of forming and using a silicon oxide film will beexplained.

Referring to FIG. 20, 1901 is a glass substrate, 1902 is a Si₃N₄ film,1903 is a channel layer of a polysilicon n-MOS having a predominantly(111)-oriented surface, 1905 and 1906 are respectively a source regionand a drain region of the polysilicon n-MOS, 1904 is a channel layer ofa polysilicon p-MOS predominantly oriented in the (111) surface, and1907 and 1908 are respectively a source region and a drain region of thepolysilicon p-MOS. Further, 1910 is a gate electrode of the polysiliconn-MOS, and 1911 is a gate electrode of the polysilicon p-MOS, 1912 is aninsulation film of such as SiO₂, BSG, or BPSG, 1913 and 1914 arerespectively the source electrode of the polysilicon n-MOS (andsimultaneously the drain electrode of the polysilicon p-MOS), and 1915is the source electrode of the polysilicon p-MOS.

It should be noted that a polysilicon film formed on an insulation filmbecomes stable, and is dense and well crystallized and thus provideshigh quality, when having the (111) surface orientation in the directionperpendicular to the insulation film. In this embodiment, 1909 is asilicon oxide film layer of the present invention having the thicknessof 0.2 μm and formed by the procedure similar to the one in the firstembodiment by using the apparatus of FIG. 19, and is formed on the (111)oriented polysilicon at 400° C. with the thickness of 3 nm.

According to the present invention, there occurred no thinning of oxidefilm at the sharp corner part of the device isolation region formedbetween the transistors, and it was confirmed that the silicon oxidefilm is formed with uniform film thickness on the polysilicon in any ofthe flat part and edge part. The ion implantation process for formingthe source and drain regions was conducted without passing through thegate oxide film, and the electrical activation was made at 400° C. As aresult, the entire process can be conducted at a temperature of 400° C.or less, and it was possible to form a transistor on a glass substrate.The transistor had the mobility of approximately 300 cm²/Vsec or morefor electrons and approximately 150 cm²/Vsec or more for holes. Further,a voltage of 12V or more was obtained for the source and drain breakdownvoltages and for the gate breakdown voltage. A high-speed operationexceeding 100 MHz became possible in the transistor having the channellength of about 1.5-2.0 nm. The leakage characteristics of the siliconoxide film and the interface state characteristics of thepolysilicon/oxide film were good.

By using the transistor of this embodiment, the liquid crystal displaydevices or organic EL photoemission devices can provide large displayarea, low cost, high-speed operation, and high reliability.

While this embodiment is the one in which the gate oxide film or thegate nitride film of the present invention is applied to a polysilicon,this embodiment is applicable also to the gate oxide film or gatenitride film of an amorphous silicon thin-film transistor (TFT), andparticularly, a staggered-type thin-film transistor (TFT), which is usedin a liquid crystal display device and the like.

Ninth Embodiment

Next, a description will be given of an embodiment of athree-dimensional stacked LSI in which an SOI device having a metallayer, a polysilicon device, and an amorphous silicon device arestacked.

FIG. 21 is a conceptual diagram of the cross-section structure of thethree-dimensional LSI of the present invention.

Referring to FIG. 21, 2001 is a first SOI and wiring layer, 2002 is asecond SOI and wiring layer, 2003 is a first polysilicon device andwiring layer, 2004 is a second polysilicon device and wiring layer, and2005 is an amorphous semiconductor device, a functional-material device,and a wiring layer.

In the first SOI and wiring layer 2001 and also in the second SOI andwiring layer 2002, there are formed digital processing parts,high-precision and high-speed analog parts, synchronous DRAM parts,power supply parts, interface circuit parts, and the like, by using theSOI transistors explained in the seventh embodiment.

In the first polysilicon device and wiring layer 2003, there are formedparallel digital operation parts, inter-functional block repeater parts,memory device parts, and the like, by using the polysilicon transistorsor flash memories explained in the sixth and eighth embodiments.

In the second polysilicon device and wiring layer 2004, there are formedparallel analog operation parts such as an amplifier, A/D converter, andthe like, by using the polysilicon transistor explained in the eighthembodiment. Optical sensors, sound sensors, touch sensors, radio wavetransceiver parts, and the like, are formed in the amorphoussemiconductor device and functional-material device and wiring layer2005.

The signals of the optical sensors, sound sensors, touch sensors, andradio wave transceiver parts that are provided in the amorphoussemiconductor device and functional-material device and wiring layer2005 are processed by the parallel analog operation part such as anamplifier or A/D converter provided in the second polysilicon device andwiring layer 2004 and using the polysilicon transistor, and areforwarded further to the parallel digital operation parts and the memorydevice parts provided in the first polysilicon device and wiring layer2003 or the second polysilicon device and wiring layer 2004 and usingthe polysilicon transistors and flash memory devices. Further, thesignals are processed by the digital processing parts, high-precisionand high-speed analog parts, or the synchronous DRAM parts provided inthe first SOI and wiring layer 2001 or second SOI and wiring layer 2002and using the SOI transistors.

In addition, the inter-functional block repeater part provided in thefirst polysilicon device and wiring layer 2003 does not occupy a largechip area even when provided with plural numbers, and it is possible toadjust synchronization of signals all over the LSI.

It should be noted that production of such a three-dimensional LSI hasbecome possible as a result of the technology of the present inventionexplained in detail in the above-described embodiments.

In the above, the description are given of the present invention withrespect to the preferred embodiments. However, the present invention isnot limited to such specific embodiments, and variations andmodifications may be made without departing from the scope of thepresent invention.

INDUSTRIAL APPLICABILITY

According to the present invention, it becomes possible to completelyremove surface-terminating hydrogen even at low temperature of about400° C. or less in continuous processing without breaking vacuum andwithout degrading the planarity of a silicon surface. Hence, it ispossible to form a silicon oxide film, silicon nitride film, and siliconoxynitride film, having characteristics and reliability superior tothose of a silicon oxide film formed by a conventional thermal oxidationprocess or microwave plasma processing, on a silicon of any surfaceorientation at low temperature of about 500° C. or less. Consequently,it becomes possible to realize a miniaturized transistor integratedcircuit having high reliability and high performance.

Also, according to the present invention, it becomes possible to form athin and high-quality silicon oxide film, silicon nitride film, andsilicon oxynitride film having good characteristics such as leakagecurrent and breakdown voltage even on a silicon surface of a corner partof a device isolation sidewall of, for example, a shallow-trenchisolation or on a silicon surface having a surface form with projectionsand depressions. Consequently, it becomes possible to achievehigh-density device integration with a narrowed device isolation widthand high-density device integration having a three-dimensionalstructure.

In addition, by using the gate insulation film of the present invention,it was possible to realize a flash memory device and the like capable ofsignificantly increasing the number of times of rewriting.

Further, according to the present invention, it becomes possible to forma high-quality silicon gate oxide film and silicon gate nitride filmeven on a polysilicon formed on an insulation film and having apredominantly (111)-oriented surface. As a result, it becomes possibleto realize a display apparatus that uses a polysilicon transistor havinghigh driving ability, and further, a three-dimensional integratedcircuit device in which a plurality of transistors and functionaldevices are stacked, which provides great technology spillover effects.

1-4. (canceled)
 5. A fabrication method of a semiconductor device on asilicon surface, comprising the steps of: exposing said silicon surfaceto a first plasma of a first inert gas so as to remove hydrogen existingon at least a part of said silicon surface in advance; and generating asecond plasma of a mixed gas of a second inert gas and one or aplurality of kinds of gaseous molecules, and forming, on said siliconsurface, a silicon compound layer containing at least a part of elementsconstituting the gaseous molecules under said second plasma.
 6. Thefabrication method of a semiconductor device as claimed in claim 5,wherein, prior to the hydrogen removing step, the silicon surface istreated by a medium including hydrogen.
 7. The fabrication method of asemiconductor device as claimed in claim 6, wherein the medium is ahydrogenated water.
 8. The fabrication method of a semiconductor deviceas claimed in claim 6, wherein the medium is a diluted hydrofluoricacid.
 9. The fabrication method of a semiconductor device as claimed inclaim 5, wherein the silicon surface is a single-crystal siliconsurface.
 10. The fabrication method of a semiconductor device as claimedin claim 9, wherein the silicon surface is a (100)-oriented surface. 11.The fabrication method of a semiconductor device as claimed in claim 9,wherein the silicon surface is a (111)-oriented surface.
 12. Thefabrication method of a semiconductor device as claimed in claim 9,wherein the silicon surface includes a plurality of different crystalfaces.
 13. The fabrication method of a semiconductor device as claimedin claim 12, wherein the plurality of different crystal faces define adevice isolation trench.
 14. The fabrication method of a semiconductordevice as claimed in claim 5, wherein the silicon surface is apolysilicon surface.
 15. The fabrication method of a semiconductordevice as claimed in claim 5, wherein the silicon surface is anamorphous silicon surface.
 16. The fabrication method of a semiconductordevice as claimed in claim 5, wherein each of the first and second inertgases is at least one kind of gas selected from a group consisting of anargon (Ar) gas, a krypton (Kr) gas, and a xenon (Xe) gas.
 17. Thefabrication method of a semiconductor device as claimed in claim 16,wherein the first inert gas is identical with the second inert gas. 18.The fabrication method of a semiconductor device as claimed in claim 5,wherein the second inert gas is a krypton (Kr) gas, the gaseousmolecules are oxygen (02) molecules, and a silicon oxide film is formedas the silicon compound layer.
 19. The fabrication method of asemiconductor device as claimed in claim 5, wherein the second inert gasis an argon (Ar) gas, a krypton (Kr) gas, or a mixed gas of argon andkrypton, the gaseous molecules are ammonia (NH₃) molecules or nitrogen(N₂) molecules and hydrogen (H₂) molecules, and a silicon nitride filmis formed as the silicon compound layer.
 20. The fabrication method of asemiconductor device as claimed in claim 5, wherein the second inert gasis an argon (Ar) gas, a krypton (Kr) gas, or a mixed gas of argon andkrypton, the gaseous molecules are oxygen (O2) molecules and ammonia(NH3) molecules, or oxygen (O2) molecules, nitride (N2) molecules, andhydrogen (H2) molecules, and a silicon oxynitride film is formed as thesilicon compound layer.
 21. The fabrication method of a semiconductordevice as claimed in claim 5, wherein the first plasma and the secondplasma are excited by microwave.
 22. A fabrication method of asemiconductor memory device that includes, on a common substrate, atransistor having a polysilicon film formed on a silicon surface via afirst insulation film and a capacitor including a second insulation filmformed on a polysilicon surface, comprising the steps of: exposing thesilicon surface to a first plasma of a first inert gas so as to removehydrogen existing on at least a part of the silicon surface in advance;and generating a second plasma of a mixed gas of a second inert gas andone or a plurality of kinds of gaseous molecules, and forming, on thesilicon surface, a silicon compound layer containing at least a part ofelements constituting the gaseous molecules as the first insulation filmunder said second plasma.
 23. The fabrication method of a semiconductordevice as claimed in claim 22, further comprising the steps of: exposingthe polysilicon surface to a third plasma of a third inert gas so as toremove hydrogen existing on at least a part of the silicon surface inadvance; and forming a fourth plasma of a mixed gas of a fourth inertgas and one or a plurality of kinds of gaseous molecules, and forming,on the polysilicon surface, a silicon compound layer containing at leasta part of elements constituting the gaseous molecules as the secondinsulation film under said fourth plasma.
 24. The fabrication method ofa semiconductor device as claimed in claim 23, wherein the first andthird inert gases are at least one kind of gas selected from a groupconsisting of Ar, Kr, and Xe.
 25. The fabrication method of asemiconductor device as claimed in claim 23, wherein the second andfourth inert gases are Kr, and the first and second insulation films areformed by a silicon oxide film.
 26. The fabrication method of asemiconductor device as claimed in claim 23, wherein the second andfourth inert gases are Ar or Kr, and the first and second insulationfilms are formed by a nitride film or an oxynitride film.
 27. Thefabrication method of a semiconductor device as claimed in any of claims22-26, wherein the first and second plasmas are excited by microwave.28. A fabrication method of a semiconductor device having a polysiliconlayer or amorphous silicon layer on a substrate as an active layer,comprising the steps of: forming, on said substrate, a silicon layer ofsaid polysilicon layer or amorphous layer; exposing a surface of saidsilicon layer to a plasma of a first inert gas so as to remove hydrogenexisting on at least a part of said surface of said silicon layer; andgenerating a plasma of a mixed gas of a second inert gas and one or aplurality of kinds of gaseous molecules, and forming, on said surface ofsaid silicon layer, a silicon compound layer including at least a partof elements constituting said gaseous molecules.
 29. The fabricationmethod of a semiconductor device as claimed in claim 28, wherein thefirst inert gas is at least one kind of gas selected form a groupconsisting of Ar, Kr, and Xe.
 30. The fabrication method of asemiconductor device as claimed in claim 28, wherein the second inertgas is Kr, and the silicon compound layer is a silicon oxide film. 31.The fabrication method of a semiconductor device as claimed in claim 28,wherein the second inert gas is Ar or Kr, and the silicon compound layeris a nitride film or an oxynitride film.
 32. The fabrication method of asemiconductor device as claimed in claim 28, wherein the first andsecond plasmas are excited by microwave.